Two areas are showing haze: the San Joaquin Valley in California and fires are burning in Louisiana along the Mississippi. Only California has elevated AQI, however, and overnight some "Unhealthy for Sensitive Groups" readings were seen in the Central Valley (left). By afternoon, the AQI returned to "Good" or "Moderate" and you can see part of the reason for the overnight haze.... humidity. By 10:30 this morning, lingering fog can be seen in the valley.
In Louisiana, MODIS saw the fires clearly along the Mississippi. And earlier this morning, a Tweep posted that Salt Lake City was "haze soup". Low PBL height in winter will do that to you. The AQI was "Moderate".
Update: November 25, 2012 22:15 EST
Satellite AOD shows very little across the US but retrievals in the San Joaquin Valley are not available. Terra MODIS saw considerable fog in the valley and in the afternoon, a light haze is seen but not retrieved in the MOD04 product due to high surface reflectivity. PM2.5 concentrations in the Valley, however, are in the Unhealthy for Sensitive Groups range and AIRNOWTech hourly PM readings are shown below.